A liquid crystal display is an important flat panel display, and one integral liquid crystal display panel comprises a backlight module, a polarizer, an upper substrate, a lower substrate and liquid crystal molecules filling a cell comprising the two substrates, wherein the upper substrate may be a color filter substrate and the lower substrate may be an array substrate.
Data lines and gate lines crossing transversely and longitudinally are formed on the array substrate. The data lines and the gate lines together define pixel units arranged in a matrix form. Each pixel unit comprises a Thin Film Transistor (TFT) switch and a pixel electrode pattern, wherein the TFT switch comprises a gate metal pattern, a source-drain metal pattern and an active layer pattern; the gate metal pattern is connected with the gate line, the source-drain metal pattern is connected with the data line and the pixel electrode pattern, and the active layer pattern is formed between the source-drain metal pattern and the gate metal pattern. A common electrode pattern may be formed on the array substrate and is used to form an electric field together with the pixel electrode pattern, and a rotating degree of the liquid crystal molecules is controlled by a change of intensity of the electric field between the common electrode pattern and the pixel electrode pattern.
Along with continuous improvement of the performance of the TFT, it is hard for the existing TFT technology to have a breakthrough. Although amorphous Silicon (a-Si), as a material of the active layer, is easy to be fabricated in a large area at low temperature and the technology is relatively mature and becomes the most widely used technology at present, the a-Si material has a band gap of only 1.7V, is opaque to visible light, has light sensitivity in a visible light range and needs to add an opaque metal mask (black matrix) to block light, which results in increased technology complicacy of a TFT-LCD, increase of cost, reduction of an ON state current of a device, and longer pixel charging time; and for large-sized display products, reliability and aperture ratio are reduced, power consumption is increased, and the performance is hard to be further improved, and therefore, the array substrate is relatively poor in display performance and high in cost.